The HTML5 video tag promises to eliminate the need for third-party plugins like Flash or QuickTime. Sadly, it’s a long way from “promises” to “delivers.” While HTML5 offers a video tag for authors to easily add videos to their webpages, it’s up to the browser to actually play that video. And that’s where the problem arises — what video codec should the browser use?

Apple is standing firm behind the H.264 video codec. But H.264 has licensing requirements, fees and is not free in any sense of the word. Mozilla Firefox supports Ogg Theora and WebM, both of which are open and free. Google’s Chrome supports all three codecs. Opera supports Ogg Theora and WebM. Microsoft has decided to support H.264 and WebM in IE9.

Microsoft’s new add-on brings support for H.264 to Firefox whether Mozilla wants it or not. The add-on parses HTML5 pages and replaces video tags with a call to the Windows Media Player plug-in. Unfortunately it’s not perfect. To deal with the different codec support in each browser, many sites use JavaScript to determine the browser’s codec support before presenting a video. If that’s the case, the new add-on won’t work because the detection code won’t see the H.264 support (the H.264 support is an add-on, not a native part of Firefox).

Ironically, native web video isn’t supported at all in Microsoft’s own browsers, regardless of the codec used (IE9 will introduce support for HTML5 video when it is released next year). Third-party developers have already created an experimental IE add-on to help current versions of IE get in on the native web video fun.

Microsoft’s add-on is far from ideal, but if you’ve been frustrated by Firefox’s lack of H.264 support, it does offer a partial solution. Hopefully, in the long run, browsers will standardize around WebM, which seems to enjoy the most widespread support (Apple’s Safari is current only browser that hasn’t pledged WebM support), but if that doesn’t happen solutions like this one may become even more common.